A measles outbreak was declared on 16 February. The majority of patients are concentrated in the Liverpool area.

But an HPA spokesman added: "We are also beginning to see cases that are further afield."

There are now confirmed, probable and possible cases in central and eastern Cheshire, Halton and St Helens, Knowsley, Sefton, and Wirral with probable and possible cases in Warrington and western Cheshire."